I will investigate the role of PROV1 in vascular pattern formation in leaves of Arabidopsis thaliana. Vascular patterning in leaves is specified by positional cues and the developing veins themselves likely act as cues for the subsequent patterning of cell types in the leaf. The gene PROV1 was recently identified, using an enhancer trap strategy, for its specific expression in young provascular cells and when cloned was found to encode a receptor-like-protein-kinase. The function of PROV1 in vascular specification and differentiation will be addressed by over-, under-, and conditionally expressing PROV1 in mature plants. The kinase activity will be evaluated, the subcellular localization will be determined by imunolocalization in situ, and interacting proteins will be identified using heterologous expression in the yeast two-hybrid system. The characterization of the role of PROV1 in vein development and insight into mechanisms which regulate vein pattern formation will result in valuable progress toward understanding positional specification during plant organogenesis.